Week 9 - Parametric study on Gate valve.

Parametric study on gate valve
Gate valve is a device used to control the fluid flow.
The flow coefficient - Cv - or the flow factor - Kv - are commonly used to specify capacities of control valves.
Flow Coefficient - Cv
The flow coefficient - Cv - is based on the imperial units system and is defined as the flow of water through a valve at 60 oF in US gallon/minute at a pressure drop of 1 lb/in2
The flow coefficient is commonly used in the U.S.
Flow Factor - Kv
The metric equivalent of the flow coefficient - Cv - is based on the SI-system and is called the
The flow factor - Kv - is defined as the flow of water with temperature ranging 5 - 30 oC through a valve in cubic meters per hour (m3/h) with a pressure drop of 1 bar
The flow factor is commonly used outside U.S.
Flow factor calculated using the formula below
Kv = Q*(SG/Delta P)^0.5
Kv is the flow factor
Q is the flow rate cubic meter per hour
SG specific gravity
Delta pressure difference in bar
Converting between Flow Coefficient Cv and Flow Factor Kv
The relationship between Cv and Kv can be expressed as:
• Cv = 1.16 Kv
• Kv = 0.862 Cv

Problem Solving steps
 Upload the geometry in space claim
 Used pull tool and extend both pipe surfaces 800 mm in x axis direction Extract the fluid volume and suppress physics for all valve components
 Move the gate valve 10 mm in z axis direction and select parametrizing option
 Start meshing using 10 mm as an element size and keep all other options as defaults
 Name face inlet and outlet
 Solution setup using viscous model k epsilon realizable scalable wall function
 Pressure based solver and gravity enabled in z axis direction
 Material selection liquid water and delete any other materials
 Boundary setting the inlet pressure at 10 pascal and outlet zero pascal
 Create plane, velocity contour and animation
 Run the calculation 500 iterations
 Change the valve open lift from 10% until 80 %
 Calculate Cv, Kv against each opening

Conclusion
 The results show that with the increase of the mass flow rate both Kv and Cv increased proportionally.
 There is another factor which might affect the simulation accuracy but it is not taken in this simulation the pipe material (friction factor), the pipe age.